Computers now have very high speed signal requirements which have resulted in a number of attempts to provide controlled impedance in the form of flexible circuitry (FEC) electrically connecting two circuit boards. In one such attempt, Middco Connectors of the Middleburg Corporation has designed a connector using FEC and hydraulic pressure to provide the required normal forces. Mechanically driven cams drive pressure plugs in windows through glands to squeeze bladders which press against the FEC.
In another attempt, the use of a memory alloy provided the means for clamping or releasing the clamping of a circuit card and for applying the normal force.
The disadvantages of these attempts include both technical and economical. Neither can provide wipe. With regard to the first mentioned connector, besides the costs involved, particular care must be given to provide a constant temperature so as not to induce pressure variations over time. With regard to the memory alloy strip, because it is a solid preform, it cannot be compliant for each individual contact pad on the film and an intervening layer of an elastomer is required. This solution has its own problem in that over time, elastomers tend to creep or relax so that the effectiveness become diminished.
A solution is in providing a connector using a conservative and traditional design wherein each discrete contact is made of a spring tempered metal whose stress relaxation and creep properties are negligible and also well understood. Further, such contacts has its own stored energy to provide a continuous and uniform force over long periods of time. However, the problem arises in the difficulty and high cost of manufacturing a mold with a large number of very thin core pins; e.g., 0.005 inches, on a dense grid; e.g., 0.050 inches with which connector housings can be made. The traditional way of making a mold would be to have a core pin holding plate in which slots or holes have to be machined accurately to contain and retain the core pin which may be for example, 0.005 inches by 0.100 inches. The plate must be of substantial strength and therefore thick, to withstand the stripping force; i.e., ejection resistances, for removing a molded plastic article from the multitude of core pins. Making such a plate is extremely difficult and costly. Accordingly, it is now proposed to provide a new method for constructing and producing a mold of such extreme complexity.